It has long been known that the dusting of seeds prior to planting with seed treatment dusts composed of an active ingredient and one or more diluent materials would improve crop yields. The active ingredients commonly used include fungicides, insecticides, and other pesticides. The diluent materials used include clays, talcs and comminuted Douglas Fir bark.
The active ingredient of the seed treatment dust protects the newly planted seed and its developing root system from attacks by harmful organisms found in the soil during the germination period. The germination period is critical because the events that occur during this period determine, to a great extent, the health and productivity of the plant that grows from the seed. The longer a seed remains in the ground before it germinates, the more vulnerable it becomes to attack by fungi and by other soil-borne pathogens and insects. A seed attacked by soil-borne organisms is less likely to produce a healthy plant. Indeed, such a seed may not produce a plant at all.
If, however, a seed germinates quickly and is protected from attack by soil-borne organisms during the germination period, there is much less chance that the plant will become diseased or will die if it does become diseased. Since the active ingredients used in seed treatment dusts protect the seed from attack by soil-borne organisms, seeds dusted with dusts containing an active ingredient have an increased chance of producing a healthy, productive plant.
The diluent materials used in seed treatment dusts act to dry seeds. Wet seeds are susceptible to attack by bacteria while they are stored awaiting planting, and a bacterial infection may weaken the seed. A weakened seed will, in turn, produce an unhealthy plant or will not produce a plant at all.
The combination of the drying effect of the diluent materials and the fungicidal or other activity of the active ingredient protects the seed during the period prior to planting and during the germination period. Seeds thus protected are much more likely to produce high crop yields.
Seeds which are dusted include the seeds of grains, legumes, onions, tubers and flowers. In particular, the dusting of tuber seeds such as potato seeds is very desirable for the production of good crops.
Potato seeds are prepared for planting by cutting a potato into several parts. The potato seed pieces are then loaded into trucks or bags and stored until planting.
When the potato is cut, the cut sides of the potato are moist. The potato secretes a substance called suberin which begins to heal the cut surface of the potato in six to eight hours if the potato surface can dry during this time. Since the potato seed pieces are piled into bags or trucks after cutting, they would, under these circumstances, remain wet for an extended period of time. These wet conditions promote bacterial growth. Further, since the suberin cannot heal the cut surface of the potato while it is wet, the bacteria can more easily gain access to the potato seed and start to decay the seeds. Seeds thus attacked by bacteria may be weakened before they are planted. Potato seeds and their neWly developing root systems are ordinarily susceptible to insects, to fungi and to other soil-borne pathogens, but a weakened seed is particularly susceptible to these harmful organisms.
If the potato seeds are dusted immediately after they are cut, the diluent materials dry the potato seeds thereby allowing the suberin to heal the cut surfaces of the potato seeds and removing an environment conducive to bacterial growth. The dusted seeds are, consequently, less likely to be weakened by bacterial decay before being planted. Further, the active ingredient in the seed treatment dust will protect the potato from attack by harmful soil-borne organisms after planting.
As mentioned above, one of the diluent materials in use is comminuted Douglas Fir bark. Comminuted Douglas Fir bark is an excellent diluent material since it is a very effective drying agent. One problem with the use of comminuted Douglas Fir bark is that it contains lignin slivers as do all coniferous tree barks, and some workers using seed treatment dusts containing comminuted Douglas Fir bark suffer minor throat, nasal and skin irritation from the lignin slivers. Another problem is that Douglas Fir bark is much more expensive than the clay and talc diluents.